Exposure meter having object and comparison gray scale means



Dec. 2o, 1949 J. L. FOUST 2,491,654

EXPOSURE METERS HAVING OBJECT AND COMPARISON GRAY SCALE MEANS F :i n

I@ S'yn WUI Q-L-*l-.J 32' v |NVENTOR. 25 Jahn i PELLET ATTORNEYS.

BY ,42 E, MMM@ f Dec. 20, 1949 J. L.. Fous'r 2,491,654

EXPOSURE METERS HAVING BJECT AND COMPARISON GRAY SCALE MEANS NVENTOR BY 2 @l Ma/@M ATTORNEYS.

Patented Dec. 20, 1949 UNITED STATES PATENT OFFICE EXPOSURE METER HAVING OBJECT AND COMPARISON GRAY SCALE MEANS John L. Faust, Madison, Wis.

Application September 6, 1946, Serial No. 695,141

(Cl. Sii-23) Claims. l

This invention relates to photographic lm exposure meters, and more particularly to an indirect'comparison type meter, as distinguished from direct comparison types thereof.

The meter of this invention is an indirect comparison type meter, as the reading of the object is separate from that of the comparison light. For this reason color filters are not as necessary as color filters generally employed with direct comparison types. The extinction points on the object and comparison scales employed can be compared even though the indicia of one scale may show (be illuminated by) light of a different color than the indicia of the other scale.

On the other hand, conventional comparison type meters use some form of spit comparison field (double field) where one eld, illuminated by the object, is compared with a eld illuminated by the comparison light. These are direct comparison meters, both elds being illuminated at the same time and the observer judging when they are of equal brightness. These meters usually use light filters so the two fields will have the same color as it is diflicult to judge their comparative illumination where their colors differ. If the object iield in such a meter is brilliantly illuminated by the object the comparison eld must be equally brilliant.

Another advantage of the meter of this invention, which it has over the direct comparison type meters, is in its use of a comparatively low intensity comparison light. With direct comparison meters, the comparison light must be bright enough to match the field illuminated by the object. With the novel meter herein disclosed, under brilliant light conditions, nearly all the indicia on the object scale may be recognizable (showing) in which case the extinction point will be many times lower in brightness than the object itself. The comparison light has to illuminate merely an extinction point on its scale. In other words, the comparison light has to be visible only. This results, in comparison with direct comparison type meters, in longer life for the lamp and lower drain upon the battery.

Still another advantage of the meter of this invention resides in its use to scan objects which are illuminated unevenly, so as to estimate their averages illumination, and use the comparison light'only once in the operation. This is done by watching the extinction point move back and :Iorth` over the object scale as readings are taken of various parts on an object. Thus, if the ex- Y tinction point moved over three of the indicia of the scale such as 3, 4 and 5, the operator could recognize 4 as the extinction point and then take the comparison reading for the purpose of calculation. On the other hand, with the use of direct comparison meters, the comparison light must be used when reading each part of the object.

An important object is to provide an electric lamp and battery containing meter which is available for use as a conventional extinction type meter, in case of battery or lamp failure.

Still another object is to provide a meter in which the comparison light has a comparatively low intensity, thus increasing the life of the lamp.

Another object is to provide a meter in which the range of illumination of an object can be judged by means of the object scale alone. This results in low drain on the battery as the latter has to be energized only once instead of for each part of the object. With the ordinary comparison type meters all readings require a comparison light.

Other objects and advantages of the invention will be apparent during the course of the following detailed description, taken in connection with the accompanying drawings forming a part of this specification, and in which drawings:

Figure 1 is a plan View of one embodiment of the novel meter, with its housing open.

Figure 2 is an elevation of one side face of the meter, with its housing closed.

Figure 3 is an elevation of the other side face thereof.

Figure 4 is a vertical, transverse section upon substantially the line 4-4 of Figure 2. K

Figure 5 is a wiring diagram for the meter of Figures 1 to 4 inclusive, as well as the meter of Figures 6 to l0 inclusive.

Figure 6 is a plan view of another embodiment of the invention with the housing of the meter open.

Figure 7 is an elevation of one side face of the meter of Figure 6, with its housing closed.

Figure 8 is an elevation of the other sidel face thereof.

Figure 9 is a vertical, transverse section upon substantially the line 9-9 of Figure 8, and a light reiiecting means in one position.

Figure 10 is a view, similar to Figure 9, but. with the light reecting means in another position.

In the drawings, wherein for the purpose of illustration are shown two embodiments of the invention and wherein similar reference characters designate like parts throughout the several views, the novel exposure meter of Figures l to 4 inclusive is designated as A and that of Figures 6 to 10, inclusive, designated as B.

The novel exposure meter A includes a housing means I6 to illuminate the interior thereof means |1 to selectively extinguish the light of the means i6 Within the housing and to reilluminate the interior thereof by the means I6; extinction type .scale means I8 Within the housing for taking obiectandcomparison light readings; and means i9 for directing the rays of light from the means I6 through at least a portion or" the means I8.

Preferably, the housing l5 comprises two vsections and 2|. The rst section '211 pi the housing |5 has a substantially flat, inner face 22, an outer face 23, parallel therewith, v'two outer end faces 24 and 25 in parallelism, and two :outer side faces 26 and 21 in parallelism. Intermediate the side faces 26 and 21, the section V22| is provided with means 29 #to retain a scale member to be subsequently described. This y'may vbe the walls of anelongated, narrow'reces's '3e preierably extending longitudinally ci' the section (and housing). Extending from the recess 35 to 'the face r2.5 is La peep .slot-for opening 3| vand extend ing from the :recess 43|) tothe tace 2 iis :a peep slot :or opening 32,. For ready insertion .of the scale member to be described, A'the recess 13l! may extend from the innerfacezZ, preferably inclined slightly with respect vto :the face T22, :as in'Figinze 4, .and'terminating shortvoi ithenuter ff'ace `23,. 2inadditiomthe Vsection may .be Iprovided La battery-.accommodating recess 32 opening `into the face 22 and :spaced from the .recess 136 `and slots 3| and '32.

As for .the second section 2|, :this is Vof substantially the same si' ze :and-generalishape ofthe section l2 Il, has asuhstantia-lly `flat, inner face 35, an `outer face 36 parallel-therewith, two outer, parallel end faces 31 and ..33 and two outer, parallel side faces 39 and 40. Intermediate the faces 33 and 40 .and .adjacent the end face 3B, is a recess 4| which extends vlongitudinally of the housing, accommodates l.a scale kmember to be described .and may .also accommodate portions .of the means .|.6 and |1,. `Extending .fromrthe recess 4| to the Iside face v39 is a .slot or peep opening 42. Preferably, the position of the vslot '42 is such that, when the sections 20 and 2] are disposed as in VFigure v2, the slot '3| of section 21|, will be adjacent slot 42 o`f section 21- 'The section `2| may also contain a battery-accommodating recess 43 extending from the face 35 and disposed so that, when the sectlons'Zl 'and 25| 'are disposed as in Figures 2, i3 vand 4,'the1'ecesses3'2 and "133 will form one recess.

1f desired, the two sections "20 `and 2| may be hingedly connected, as along one end Iof' each, by a leaf hinge 44.

Means i6 to illuminate the interior of the housing I5 may be an electric lamp 45, set into a socket portion 4B ycarried by the section 2| within the recess 41|, a suitable source of electricity as a'battery -41 which is, preferably, a dry battery, contained in the combined recess -32 and 43, a suitable lead 156 from the battery 4i111 `to the socket portion 156 containing the lamp v546, a suitable lead 49 from the battery 41 to a contact ci the means f| 1 (which may be a conventionalfelec tric switch 55, `having a iixe'd contact '5| and 'a movable contact 52, preferably `comprising fa leaf of springy metal, vboth 'secured to a suitable base 53 and contained in the recess 2H) with va suitable switch `button 55 extending 'through 'an fopening in the section 20 landfadaaipted to vcontact the movable contact 52 when the sections 25 and 2| are disposed as in Figures 2, 3 and 4, and a lead 55 from another of the contacts of the switch 5i), to the socket portion 45.

The extinction type scale means or gray scale means I8 in the form A, comprises the two scale members 66 and 5|. Both are indicia-bearing extinction type scale members, preferably ccmprising strips :62 :of transparent material, such as glass, containing suitable indicia 63, as consecutive i'lgures (a row of consecutive gures l to 3 inclusive is shown for example, on each scale. In the example shown, the scale mem- ;ber i60 provides an indicia-bearing extinction type object scale means, since it is disposed in "the recess Sii and may be seen through either slot 3|;or .32 but .is'intended to be viewed through slot 3|, and the scale member 6| provides an indicia-bearing extinction type comparison scale means, since it is disposed in the recess el and may be seen vthrough the slot 42,. vBoth strips 62 :are so constructed and arranged that they may be uslid into their respective recesses. In the case of 'that portion of .the recess 3d extendn ing from the finner face 22, any suitable narrow strip '-64 of opaque material may be inserted in the mouth of vtl'rerecess 55, 'after the strip 62 of the member 66 has been inserted, to block out light rays vfrom the lamp d5 and prevent the strip 62 from dropping out. In the case of the strip 6,2 of the member 6|, :a suitable frame 65 secured to the section 2i may be provided to irictionally grip `rthe end edge portions of Vthe strip 62 and-preventit from dropp ng down or out.

Theextinotion type-or gray .scale means used in this meter are `of conventional construction and `are Well known in conjunction with visual extinction vmeters. With this type of scale some of the "indicia, as the indicia 63, will be invisible under normal light conditions because of the graduated Vnature of the scale and the dimmest of the visible indicia 63 is herein termed the extinction point.

Means i3 for directing the rays of light from the lamp of the means |23 through at least a portion-oi" `the means it, may be thewall surfaces of the recess 'fil and that portion of the inner face V22 covering the mouth or' the recess fil, which may have light-reflecting qualities imparted in any well known way such as by'a coating of suitably colored 'paint Light rays from the lamp 65 will be reiiected from'these surfaces and the said inner face portion through the adjacent extinction type comparison scale means and thence through the slot i2 to the Veye of an observer peeping into the slot 52. AI-Iowe'ver, as is apparent, these -light rays cannot enter the slots 3| and'32jbecause of the inner face -22 of the section 26 which forms a -wall ofthe recess lll when the twofsections 25 and 2| are in face-to-face contact.

Referring now tothe kform ZB, shown in Figures 6 to 1-0 inclusive, this invention includes a housing 1i), means 16 -lto illuminate the interior thereoi, means |1 'to .selectively extinguish the light of the vmeans i6 rwithin the .housing and reilluminate the interior thereof by the means it; extinction type lscale means '1| within the housing i5 for taking object and comparison light readings; and means 12 for directing the .rays of .light from the lmeans I5 .through at least portions corresponds with the first section 20, has a substantially flat, inner face 11, an outer face 18, parallel therewith, two outer end faces 19 and 80, in parallelism, and two outer side faces 8| and 82, also in parallelism. Extending inwardly from the inner face 11 is a first recess 83, preferably adjacent the end face 80, and, spaced from the recess 88, a battery accommodating recess 89, adjacent the end wall 19 and corresponding with the recess 32.

The second section 16 corresponds with the second section 2| of form A, is of the general shape of the section 15, and includes a nat, inner face 85, an outer face 85, parallel therewith, two end faces 81 and 88, in parallelism, and two side faces 89 and 9D, in parallelism. Intermediate the faces 89 and 90 and adjacent the end face 88 is a recess 9| which extends longitudinally of the housing, accommodates scale member to be described and may also accommodate portions of the means I6 and i1. Extending from the recess 9| to the side face 89 is a slot or peep opening 92. Extending from the recess 9| to the side face 99 is a second slot or peep opening 93 aligned with the slot 92. The section 1%, like the section 2| and section 15, may contain a battery accommodating recess 94 extending from the face 85 and so disposed that, when the sections 15 and 15 are disposed as in Figures '7 to l0 inclusive, the recesses 84 and Sli form one recess. In ad* dition, when the sections are so disposed, the re cesses 83 and 9| form one recess.

If desired, the two sections 15 and 15 may be hingedly connected, as along one end of each, by a leaf hinge 44.

Means i6 and l1 have been described in connection with the form A. The socket portion 49 for the electric lamp l5 as well as the switch 50, may be mounted upon the face 85 of the section 16, as in Figure 6, and extend into the recess 83 when the sections 15 and 'l5 are disposed as in Figures 6 to l0 inclusive. The battery 41 may be disposed within the recess formed by the combined recesses 84 and 94. The wiring diagram of Figure 5 is, of course, applicable to form B.

The extinction type scale means 1| of form B comprises a scale member which provides both an extinction type object scale means and an extinction type comparison scale means. Preferably it is exactly similar to either of the scale members 60 and 5I, and comprises a strip 62 of transparent material such as glass, containing suitable indicia 53. as consecutive figures (a row of consecutive iigures l to 8 inclusive as shown, for example). This member IDD is disposed within the recess 9i and may be seen through either slot 92 or 93 but is intended to be viewed through slot 92. The strip 52 is constructed and arranged so that it mav be slid into the recess 8|, as a suitable frame |0| secured to the section 16 may be provided to frictionally grip the edge portions of the strip 82 and prevent its accidental dislodeement. The strip 62 covers the mouth of the slot 92.

Means 12 for directing the rays of light from the lamp of the means through at least a portion of the means 1|, may be a nap or movable wall shown particularly in Figures 6, 9 and l0. It may be hinged, as at |08, to the wall of the recess 9| nearest the side face 99 and adjacent the inner face 85. Normally, the movable wall |95 is disposed with the plane of its under face |99 coincident with the plane of the upper faces of the slots 92 and 93, so that it does not impede the View through the slots 92 and 93. It

may be retained in this position by a leaf spring |01, having one end |08 secured to the movable wall |05, near the hinge of the latter and bow downwardly to the oor of the recess 9|. A suitable plunger |09 extending from the face 18 of the section 15 into the recess 9|, when the two sections 15 and 15 are together, as in Figures 6 to 10 inclusive, is adapted to contact the wall |05, above the spring |91 to urge the wall downwardly as in Figure l0, when the plunger |99 is depressed from its position in Figure 9 to its position in Figure 10. 0f course, when pressure is released upon the plunger |09, the wall |05 will spring up to its position in Figure9. This movable wall l95, when in its position in Figure l), blocks oi light rays traversing the slot 93 from traversing the slot 92 but, if the lamp 45 be now lighted, rays from the lamp will be reflected from the surfaces of the recess formed by the combined recesses 83 and 9| and from the upper surface of the wall |95, through portions of the means 1|, and the slot 92.

In use, the operator holds either meter about twelve inches from the eyes and reads the object with the object scale functioning the same as a conventional extinction meter. He then iliuminates the scale functioning as a comparison scale and reads the comparison light (notes the extinction point) and then calculates the light value from these two readings.

With reference to the scale members described, if the comparison gray scale member is so graduated that each of the indicia, following the nu meral l, is only one half as transparent as the preceding numeral, and the comparison light has an intensity of 128 foot candles, the numeral 1 will show about the full intensity, the numeral 2 will show 64 foot candles, the numeral 3 will show 32 foot candles, the numeral 4 will show i6 ioot candles and so on. What this comparison scale actually does is to show the light value at the lower limit of sensitivity of the observers eye to the moment when he makes the reading.

The object gray scale member is graduated in the same manner but its illumination depends upon the illumination of the object. Now assuming that the observer sees the numeral 3 on the object scale as the extinction point. .As this numeral 3 transmits only one fourth of the light from the object, he knows that if he can nd its value he can calculate the illumination of the object as being four times as great, so he refers to the comparison light scale member. He may see the numeral 4 on the comparison scale mem ber as the extinction point. As this numeral 4 has a set intensity of 16 foot candles it indicates that the numeral 3 on the obiect scale member has an intensity of 16 foot candles and so he calculates that the object has an intensity of 64 foot candles.

Different observers will get the same reading with this novel meter even though their eyes differ in sensitivity because, if their eyes are less sensitive on one scale member, they will also be less sensitive on the other. A reading of 2 on the object scale member and 3 on the comparison scale member will have the same result as 3 on the object scale member and 4 0n the comparison scale member.

The word "reading as herein used means the object, the illumination of which is to be ascertained or evaluated, through the object scale and noting the extinction point or noting the extinction point on the comparison scale when it is illuminated by the comparison light, or both.

Various `changes may be made to the 4forms of the invention herein shown and described withont departing from the spirit of the invention or the scope of the claims.

What is claimed is:

l. In an extinction type exposure meter, a housing, calibrated gray scale means mounted in said housing in stationary position, said housing comprising a frame deiining an aperture affording visual access to the whole of lone side of said scale means, a port vin said housing for receiving light from the :source to be measured, means establishing a light passageway from said port to a whole Vrange of values on the other side of said scale means, a source of light of iixed intensity within said housingymeans establishing alight path from said source to a whole range of values on lsaid other side of said scale means and a partition for separating the light which passes to said other vside of said scale means from said xed intensity light source from that which passes to said other side of said scale means from said light receiving port.

2. In an `extinction type exposure meter, a housing, a first `calibrated gray scale mounted therein in stationary position, a light port for receiving light from the source to be measured., means Aestablishing a light path from said port to the Vwhole of one side of said iirst gray scale, said housing comprising a frame defining an aperture affording visual access to the whole of the other side of said rst gray scale, a source of light of xed intensity, a second gray scale and means establishing .a light path between said source of light of Iixed intensity and the whole of one side of said second scale, said housing also comprising a 'second frame 'dening an aperture aording visual accessto the whole of the other side of said second scale.

3. In an extinction type exposure meter, a housing, a gray scale mounted in fixed position in said housing, said housing comprising a frame dening an aperture affording visual access to the whole of one side of said gray scale, a port in said housing for receiving light from a source to be measured, ka light source of fixed intensity, means establishing a passageway from said port and said source to the whole of the other side of said gray scale and a light valve in said passageway movable from a rst position blocking only Si the light path from said port to said other side of said Agray scale to a second position blocking only the light path from said fixed intensity source to said other side of said .gray scale.

4. In an extinction type Aexposure meter, la housing comprised of two parts marginally articulated, a iirst calibrated gray scale mounted in stationary position in the iirst of said parts, a light port in said iirst part for receiving light from the source to be measured, said `rst part defining a light path from said port to the Whole of one side of said grayscale and comprising a frame deiining an aperture `affording visual access to the whole of the other side of said gray scale, a source of light of nxed intensity in the second part of said housing, a second gray scale in the second part of said housing, said first and second parts of said housing together establishing a light path between said source of light of iixed` intensity and the Whole of one side of said second scale, said second part comprising a second frame deiining an aperture affording visual access to the whole of the other Vside of said second scale, and a battery for energizing said light source, said two parts together defining a socket for the -accommodation of said battery.

5. In an extinction type exposure meter as claimed in claim 3, a spring normally resiliently biasing said light valve to said second position and an operating rod for moving said light valve to said first position against the bias of said resilient means.

JOHN L. FOUST.

REFERENCES CITED y'Ihe following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,385,940 Ellicott July 26, 1921 1,437,399 'Comstock Dec. 5, 1922 1,450,055 Drew June 26, 1923 1,918,206 Ermisch July 11, 1933 2,066,605 Billings Jan. 5, 1937 FOREIGN PATENTS Number Country Date 132,246 Austria Mar. 10, 1933 137,768 Austria 1-; May 25, 1934 

